Halbleiter-Nanostrukturen und -Quantensysteme

Forschungsgebiet

Our group explores a wide range of topics related to the fundamental physics of nanostructured materials and their quantum-electronic and -photonic properties. We study the unique electronic, photonic and quantum properties of materials patterned over nanometer lengthscales and explore how sub-components can be integrated together to realise entirely new materials with emergent properties. This convergence of materials-nanotechnology, quantum electronics and photonics is strongly interdisciplinary, spanning topics across the physical sciences, as well as materials science and engineering.

Ausgeschriebene Angebote für Abschlussarbeiten an der Arbeitsgruppe

Nuclear Magnetic Resonance Microscopy

Nuclear Magnetic Resonance Microscopy

Magnetic resonance imaging (NMR/MRI), is one of the most powerful techniques to record three-dimensional images of nearly arbitrary samples. Current devices, such as those found in hospitals, cannot record details smaller than 1mm.

Our group aims to push MRI to a microscopy technique by improving its spatial resolution down to the sub-nm range, the scale of single atoms. This ambitious goal has recently become a realistic prospect by a new generation of quantum sensors for magnetic fields. They are based on the nitrogen-vacancy (NV) color defect in diamond and could detect fields as small as the NMR signal of a single molecule [1,2].

We are looking for a MSc student to develop the next generation of our chip-scale NMR spectrometers, and to perform experiments on magnetic resonance imaging with a spatial resolution in the nanoscale range.

Techniques:

* You will learn to fabricate microscale electromagnets in one of our clean rooms, and optimize our fabrication techniques for your project and others.

* You will design a sensor chip for microscale NMR detection and upgrade software and optics of one of our setups to perform the experiment.

* You will design, implement and analyze quantum control protocols to record nanoscale MRI images.

Probing single and multiple photons with modular superconducting nanowire detectors

Within the last years, superconducting single photon detectors (SSPDs) have proven to be one of the most versatile detectors for visible to infrared wavelengths. They outperform other single photon detectors in terms of detection efficiency (ca 90%), timing resolution (<10ps) and dark count rates (<1cps) and can be modified to detect the number of photons simultaneously hitting the detector (photon-number resolution, PNR) [1]. They can be integrated into on-chip photonic circuits, making them highly promising for future chip-based optical quantum applications.

In this project we aim at adding photon-number resolving capabilities to optical waveguide-integrated SSPDs to detect multi-photon states in optical cavities. We will use established techniques to sputter thin NbTiN and WSi superconducting films and pattern them using e-beam lithography to fabricate the superconducting detectors. These detectors will be tested and characterised at cryogenic temperatures in an optical microscopy setup to probe the fundamental detection mechanisms. We will implement a pixel-based photon number resolving technique and study the interaction of these pixels on the picosecond timescale using ultrafast lasers both in the visible as well as in the infrared regime.

During the project, you will work in close collaboration with a team of Ph.D. students and postdocs, therefore, teamwork is crucial on this project. Some experience in the areas of optics, electronics, programming or cleanroom fabrication will be beneficial, but secondary to your personal motivation and commitment to this fascinating project. You will gain skills and knowledge and probably become an expert in various scientific research tasks, including but not limited to thin-film deposition techniques, nanoscale cleanroom fabrication and state-of-the-art electro-optical measurements at cryogenic temperatures.

[1] F. Natarajan et al. Supercond. Sci. Technol. 25 063001 (2012)

You should:

(1) Be highly motivated, (2) Be practically minded, (3) Enjoy working with state of the art optics and with control electronics / computer control and be capable of programming (e.g. Labview, C++ , Python) (4) Be willing to work as part of a small team in a dark lab in the summertime....

You’ll get:

(1) experience of performing sophisticated optical spectroscopy in state-of-the-art laboratories and (2) a sound understanding of the physics of superconducting thin films and quantum light detectors and, hopefully, (3) a nice paper in a journal.